In an analysis posted on its website, S&P explicitly stated that it "takes no position on the mix of spending and revenue measures," however that is a fact that will likely be glossed over by the self-described mainstream media.

There is much more in the analysis, but since you won't likely see this info in the big media outlets, I am reproducing portions of the report which repeatedly mention excessive spending as a problem:

The outlook on the long-term rating is negative. We could lower the long-term rating to 'AA' within the next two years if we see that less reduction in spending than agreed to, higher interest rates, or new fiscal pressures during the period result in a higher general government debt trajectory than we currently assume in our base case. [...]

We lowered our long-term rating on the U.S. because we believe that the prolonged controversy over raising the statutory debt ceiling and the related fiscal policy debate indicate that further near-term progress containing the growth in public spending, especially on entitlements, or on reaching an agreement on raising revenues is less likely than we previously assumed and will remain a contentious and fitful process. [...]

Republicans and Democrats have only been able to agree to relatively modest savings on discretionary spending while delegating to the Select Committee decisions on more comprehensive measures.[...]

Standard & Poor's takes no position on the mix of spending and revenue measures that Congress and the Administration might conclude is appropriate for putting the U.S.'s finances on a sustainable footing. [...]

Even assuming that at least $2.1 trillion of the spending reductions the act envisages are implemented, we maintain our view that the U.S. net general government debt burden (all levels of government combined, excluding liquid financial assets) will likely continue to grow.

As you can see above, so-called "entitlement spending" on Social Security and Medicare is mentioned as a major concern in the piece. For reference, see the following chart from the Government Accountability Office:

Also for reference, please also see a graph from the Heritage Foundation which illustrates U.S. spending under former president George W. Bush and current president Barack Obama: